Moisture vapor permeable backing materials having a moisture vapor permeable pressure sensitive adhesive are disclosed by Hodgson in U.S. Pat. No. 3,645,835. The backing materials disclosed therein are synthetic polymers which are continuous and nonpermeable to liquid water. The adhesive materials are also permeable to moisture vapor. There is no disclosure of a discrete segmented block copolymer additive to either the backing material polymer or the adhesive material polymer to increase the moisture vapor transmission capability.
Other materials have been suggested for use as additives to polymers used in bio-medical devices, however, not for the purpose of enhancing moisture vapor transmission. For example, Nyilas in U.S. Pat. No. 3,562,352 suggests cross-linked thermosetting polysiloxane-polyurethane block copolymers for use as blood contact surfaces of bio-medical devices. The technique disclosed therein includes fabricating the entire blood contacting device from such block copolymers or coating such devices with the copolymers.
Minor amounts of block copolymers including segments of polydimethylsiloxane and blocks of polycarbonate, polystyrene, poly-(2,6-diphenyl-1,4-phenyleneoxide), and polyamide-imide have been blended with base homopolymers for modifying the surface properties of the homopolymers. Gaines, et al. in U.S. Pat. No. 3,961,122 suggest using such surface modified polymers as thin films while Gaines, et al. in U.S. Pat. No. 3,686,355 suggest a variety of uses, including bulk uses.
Flexible, soil resistant sheet material comprising a fibrous mat covered with a polyurethane composition is disclosed in U.S. Pat. No. 3,423,359. The polyurethane composition contains 0.1 to 5% of a surface active agent comprising a polyethylene oxide hydrophilic component and a hydrophobic component selected from polyalkylene oxides (except polyethylene oxides), aliphatic polyesters and mixtures thereof. No hydrophobic soft blocks such as polydialkylsiloxanes are disclosed as part of the surface active agent.
Block copolymers useful in the treatment of fibrous materials to improve soil release properties are disclosed in U.S. Pat. No. 3,565,845. The block copolymers are not mixed with a base polymer when used to treat the fibrous materials.
Holker et al., U.S. Pat. No. 4,367,327, disclose "a monolithic, breathable polyurethane textile coating." However, the invention is directed to a limited composition of matter claims and as a result, in actual commercial applications, there are some serious shortcomings. It discloses only one polyurethane that is used both as the top coat and the adhesive and is based only on polyethylene oxide glycol (PEO) soft segments. The use of a trifunctional isocyanate as a crosslinker is also claimed. In actual applications, since the inventive medium has only the hydrophilic PEO in its backbone, the coating swells too much, especially during washing. This leads to delamination from the fabric. In contrast, the present invention has two chemically different compositions as the adhesive and the top coat is based on at least three soft segments, can use a diisocyanate as well as a polyisocyanate as a crosslinker during coating and, in addition, has different coating formulations involving stabilizers, surface active additives, etc. to obtain a premium performance from the coated fabric.
Ward et al., U.S. Pat. No. 4,686,137, is directed only to the coated fabric. It also uses only one polyurethane composition as the adhesive and the top coat. It does not describe the coating formulation (crosslinkers, etc.). The coating polymer described has at least one hard segment (urea or urethane) and at least one hydrophilic (PEO) and one hydrophobic soft block (polytetrahydrofuran, also called "PTMO"). Furthermore, the polymer may contain up to 2% by weight polydimethylsiloxane (PDMS). A superficial structural similarity between the structure described in Ward et al. and that in the present application is deceiving as the preferred polymers in the present application are cycloaliphatic 4,4-bis(isocyanatocyclohexyl)methane (HMDI) based instead of aromatic p,p'-diphenylmethane diisocyante (MDI) and the chain extender is preferably a long chain branched diamine instead of short ethylene diamine (ED) or 1,4-butanediol (BD). In addition, the present invention clearly distinguishes between a top coat and an adhesive polymer and describes a well defined coating formulation. The amount of PDMS in the top coat polymer is greater than 2% by weight. The adhesive layer has reactive end groups. In addition, in actual commercial applications, the Ward system does not perform as described. Even if one crosslinks the structure shown in Ward during coating, it still does not perform, especially due to high surface tackiness and poor washability.
Ward et al, U.S. Pat. No. 5,120,813, is similar to the Ward '137 patent; only the claims are directed to the polymer composition and to the films. No improvement over the '137 system is achieved.
Uhlmann et al., U.S. Pat. No. 4,052,495 describe a method to prepare "release compositions" for non-cellular polyurethanes using low levels (0.5-5% by weight) of siloxane alkylene oxide copolymer additives. In contrast, the present invention is directed to achieve exactly the opposite result, i.e., to permanently bond a polyurethane formulation onto a substrate.
Pechhold, U.S. Pat. No. 4,120,850 describes a polyurethane prepared by using a "copolymer of tetrahydrofuran and ethylene oxide or propylene oxide containing 20-70% ethylene oxide" as a soft segment together with a diisocyanate (MDI) and a diol (1,4-butanediol or hydroquinone-.beta.-hydroxyethyl ether) as a hard segment. All reactions are carried in bulk.
The present application, in contrast, has PTMO and PEO, together with at least another soft segment but these segments are always separated from each other with a diisocyanate or a hard segment group. They are never directly linked to one another. Furthermore, in terms of field of applications, Pechhold never mentions coated fabrics.
Matsumoto et al., U.S. Pat. No. 4,945,149, claim a coating composition for forming a substantially non-porous moisture permeable coating layer or fiber of a hydrophilic polyurethane resin comprising an isocyanate terminated prepolymer with a viscosity of &lt;10,000 cps (no solvent) and a curing agent which is a diol or diamine. In contrast, the present invention has a high molecular weight polymer which is not isocyanate end capped. Moreover, no unreacted isocyanate is left in the present system that has, if any (as in the adhesive), hydroxyl end groups.
Sakhpara, U.S. Pat. No. 4,924,214, describes a system similar to Matsumoto above. It claims an isocyanate terminated low viscosity prepolymer based on poly (alkylene oxide) glycol soft segments. No other soft segments are utilized. No chain extenders are used or claimed. The main concern of the invention is the viscosity of the 100% active system (no solvent is used).
Driskill et al., U.S. Pat. No. 4,925,732, describe a breathable adhesive, fabric coating prepared by using the adhesive and a microporous poly(tetrafluoroethylene), and applications of the laminates. The adhesive described has only one component, i.e., a hydrophilic block polyurethane consisting of PEO soft segments (Mn 600 to 3500 g/mole), a hard segment consisting of a polyisocyanate and a chain extender that has a molecular weight of less than 500 g/mole and optionally a chain terminator. The laminates described are not stretchable in contrast to the laminates in the present application.
Gould et al., U.S. Pat. No. 5,120,816, describe a polyurethane urea polymer and the application of the non-crosslinked film formed from the polymers in the medical field. No textile coatings are described or claimed. Moreover, the film formed in Gould is used as is, whereas in the present invention, it is always preferred to have a fabric substrate.
Rautenberg et al., U.S. Pat. No. 4,761,324, describe the preparation of a laminated elastic fabric coated with a breathable, stretchable polyurethane film using a discontinuous adhesive. They do not have any (well defined) compositional claims on the laminate or the adhesive. The product has very poor breathability as further evidenced by the need to put a very thin layer of the top coat. In addition, Rautenberg requires the use of a discontinuous adhesive (which is not breathable) in contrast to our solid continuous film. The present invention is not limited to a thickness of &lt;25 microns, either.
Waterproof, moisture vapor permeable (breathable) textile coatings have become a very important part of our daily lives due to the comfort provided by these materials. Applications of these coated fabrics cover a wide range of diverse fields, including but not limited to the following listed below:
i. outdoor garments, such as sportswear and activewear (e.g., light jackets, jogging suits, skiwear, etc.), PA1 ii. heavy duty rainwear (e.g., policemen, postal carriers), PA1 iii. industrial clean room garments (such as electronics and pharmaceutical production facilities), PA1 iv. breathable, fluid barrier medical garments (such as surgical garments, bedsheets, surgical drapes, etc.), PA1 v. protective military garments, PA1 vi. tents and sleeping bags, PA1 vii. wound dressings, PA1 viii. protective marine (yacht and boat) covers, PA1 ix. natural and synthetic leather coatings, PA1 x. glove inserts, PA1 xi. shoe insulation. PA1 1. high water vapor transmission rate, PA1 2. totally waterproof (also impermeable to other fluids, especially blood), PA1 3. soft, dry touch, PA1 4. good film strength (mechanical integrity), PA1 5. good adhesion to the fabric, PA1 6. highly stretchable, PA1 7. good drape, PA1 8. machine washable (including industrial washing with hot water and bleach), PA1 9. dry cleanable, PA1 10. good overall durability (abrasion resistance, thermal, hydrolytic, oxidative and ultraviolet stability), PA1 11. windproof, PA1 12. lightweight, PA1 13. fire retardant, PA1 14. barrier to microbes and/or other microorganisms (medical applications), PA1 15. good sewability, PA1 16. tapeability of the seams. PA1 1. Adjustable to various coating techniques PA1 2. Easily compoundable with PA1 3. Ease of applicability to various fabrics: PA1 R.sup.2 is poly(ethylene oxide) of molecular weight 400 to 8000 g/mole, PA1 R.sup.3 is poly(tetramethylene oxide), poly(propylene oxide), polybutadiene or polyisobutylene of molecular weight 500 to 3000 g/mole, PA1 R.sup.4 is a polyester glycol (such as poly(butylene adipate), poly(neopentyl adipate), etc.) with a molecular weight of 500 to 3000 g/mole, PA1 R.sup.5 is a bivalent aliphatic, linear or branched hydrocarbon having 2 to 20 carbon atoms, PA1 R.sup.6 is a linear or branched hydrocarbon chain having 2 to 20 carbon atoms or an ether having 2 to 20 carbon atoms, PA1 R.sup.7 is a hydrogen or an alkyl having 1 to 4 carbon atoms, PA1 X is an oxygen atom or ##STR2## group where R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, PA1 Y, Z represent a hydrogen atom or a hydroxy group, with the proviso that at least Y or Z is a hydroxy group, PA1 (a), (b), (c), (d), and (e) represent the average repeat units in the polymer backbone, PA1 (a), (b), (c), and (d) are numbers up to 10, PA1 (a), (b), and (c) each must be at least 1, PA1 (e) is a number up to 50. PA1 R.sup.2 is poly(ethylene oxide) of molecular weight 400 to 8000 g/mole, PA1 R.sup.3 is an aliphatic linear or branched hydrocarbon having 2 to 20 carbon atoms, PA1 R.sup.4 is a poly(tetramethylene oxide), poly(propylene oxide), polybutadiene or polyisobutylene with a molecular weight of 500 to 3000 g/mole, PA1 R.sup.5 is a polycaprolactone segment with a molecular weight of 500 to 5000 g/mole, PA1 R.sup.6 is an alkylenoxy group having 1 to 12 carbon atoms, PA1 R.sup.7 is an alkoxy group having 1 to 20 carbon atoms or a substituted alkylamine such as dibutylamine, PA1 X is an oxygen atom or ##STR8## group where R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, PA1 (a), (b), (c), (d), and (e) represent the average repeat units in the polymer backbone, PA1 (a), (b), (c), and (d) are numbers up to 10, PA1 (a), (b), (c), (d) and (f) each must be at least 1, PA1 (e) is a number up to 300, and PA1 (f) is a number up to 10.
In principle, there are two different kinds of waterproof, breathable polymeric textile coatings. The first types, which are also termed "microporous coatings," provide breathability due to the presence of tiny pores present in the films. These pores are too small for water droplets to go through, however, large enough for water vapor to pass, thus providing a waterproof, moisture permeable membrane. The second type, or next generation of breathables, are called "monolithic coatings." They are solid films (not having any micropores) and therefore they are impermeable to water. Their breathability comes from the specific design of their molecular structure and molecular architecture.
Examples of microporous, waterproof, breathable textile coatings include:
______________________________________ Gore-Tex Microporous Tetrafluorethylene W. L. Gore, USA Entrant Microporous Polyurethane Toray, Japan Ultrex Microporous Polyurethane Burlington, USA Breathe Microporous Polyurethane UCB, Belgium Exeltech Microporous Polyurethane Unitika, Japan Celtech Microporous Poly(amino acid) Unitika, Japan ______________________________________
Examples of monolithic, waterproof, breathable textile coatings include:
______________________________________ Sympatex Monolithic Polyester Akzo, Netherlands Witcoflex Monolithic Polyurethane Baxenden, U.K. Bion-II Monolithic Polyurethane Goldschmidt, Germany ______________________________________
In addition to being waterproof and highly moisture vapor permeable, there are many other requirements for these coatings depending on the field of application and/or the substrates they are coated on. As an example, when highly stretchable "Lycra-Spandex" is used as a substrate for these coatings, the coating itself must (at least) stretch as much as "Lycra-Spandex". When applied on reusable medical garments, the coating must be stable against washing with hot water and bleach and also must be steam sterilizable for up to 50 cycles or more. Most of the products on the market, including the coatings listed above, are not suitable for such applications.
In addition to the performance requirements of the coated fabrics, there are also many process related requirements during the commercial coating process which eventually determine the quality, aesthetics and the overall performance of the system. The following is a list of various performance related requirements from these waterproof, moisture vapor permeable coatings:
Process related requirements during commercial coatings:
i. direct coating, PA2 ii. transfer coating, PA2 iii. lamination, PA2 iv. spray coating, PA2 v. dipping. PA2 crosslinkers or curing agents (e.g., polyisocyanates, aziridines), PA2 pigments (e.g., titanium dioxide), PA2 fillers (e.g., carbon black), PA2 other specialty additives (e.g., antimicrobial agents, flame retardants), PA2 levelling agents (e.g., silica), PA2 surface active agents (e.g., silicone oil, fluorochemicals), PA2 stabilizers (e.g., thermal, hydrolytic, oxidative and ultraviolet stabilizers). PA2 woven, PA2 non-woven, PA2 knit, PA2 melt blown substrates.
It is fairly difficult to combine all these properties into one coating material. For example, although microporous tetrafluoroethylene (e.g., "GoreTex") has very good breathability and waterproofness, it is not stretchable. Similarly, the monolithic polyester ("Sympatex") suffers from poor stretchability. Commerically, these two materials are offered as thin films so can only be coated onto the fabric by lamination. It is also impossible to compound these materials with various additives listed above since they are offered as ready-to-laminate films. Microporous products in general also suffer from being poor barriers to various microorganisms. Another weakness of the presently available waterproof, breathable textile coatings (from respective technical data sheets and hang-tags) is the fact that they can be machine washed only with warm water (usually, about 40.degree. C.) and with a mild detergent (without bleach). They can be tumble-dried at fairly low temperatures. However, as we have discussed above, especially for medical applications, one does not only need to wash them with hot water and with the presence of bleach, but also to steam sterilize them at temperatures exceeding 120.degree. C.